四川盆地川中地区盐亭-潼南海槽台缘带二叠系长兴组储层特征及成因探讨
Reservoir Characteristics and Genesis of the Changxing Formation on the Margin of Yanting-Tongnan Trough, Central Sichuan Basin

四川盆地长兴组发育优质生物礁滩储层，是重要的勘探层系.目前，缺少对其储层特征和成因的研究.以岩石特征分析为基础，结合区域地质研究、镜下鉴定、阴极发光、Sr、Fe、Mn元素和C、O、Sr同位素等地球化学特征分析，对盐亭-潼南海槽台缘带礁滩体储层岩石学特征、地球化学特征等展开了系统研究.受盐亭-潼南海槽台缘带控制，川中地区礁滩体呈规律性展布.海槽东侧广安-公山庙台缘带主要发育生物礁，以生物礁滩复合体中的礁顶滩及礁内滩白云岩为主要储集岩，储集空间主要为粒间孔及生物格架孔，白云岩化程度高；其单层厚度薄，分布广.海槽西侧生物礁不发育，以生屑滩为主，储层以生屑灰岩为主，孔隙主要为粒间溶孔、晶间孔、溶缝等；储层单层厚度较薄，累计厚度较大，分布范围比较广.埋藏白云石化是盐亭-潼南海槽台缘带白云岩储层的主要成因，埋藏期封存于长兴组地层中被淡水改造了的海水及来自于飞仙关组底部泥页岩的压实水是礁滩储层白云石化的主要流体来源；长兴末期存在的区域性暴露剥蚀叠加埋藏溶蚀改造是岩溶储层的主要成因.盐亭-潼南海槽台缘带优质储层受海槽台缘带、埋藏白云石化、长兴末期暴露剥蚀叠加埋藏溶蚀改造多因素共同控制，储层累计厚度较大，分布广，为规模有效储层.
The Permian Changxing Formation is considered as one of the key exploration strata in Sichuan Basin, which develops high-quality reef-bank reservoirs. At present, there is a lack of study on the reservoir characteristics and formation. Based on the study of regional geology, rock characteristic analysis, microscopic identification, cathodoluminescence image detection, combined with determinations of trace elements and isotopes such as Sr, Fe, Mn and C, O, Sr, the petrological and geochemical characteristics of reef-shoal reservoirs on the margin of the Yanting-Tongnan Trough are systematically investigated in order to reveal the genesis of the reservoir. The reef-shoal complexes are regularly distributed in the central part of Sichuan under the control of the platform margin of Yanting Tongnan trough. The reefs are mainly distributed in the Guang'an-Gongshanmiao platform margin, east of the trough, with bioclastic shoal dolostone in the reef-shoal complex as the main reservoir rock. The porosity types of the shoal reservoir consist mainly of intergranular pore and bio-framework pore with high dolomitization degree. The bioclastic dolostone is thin and widely distributed. In comparison, bioclastic shoal rather than the reefs is developed in the western side of the trough, and the bioclastic limestone is the main reservoirs with dissolved intergranular pores, intercrystalline pores and dissolved fractures. Despite its thin single layer, the cumulative thickness of the reservoir is large and its distribution is wide. It was indicated that buried dolomitization is the main origin of dolomite reservoir in Yanting-Tongnan area, and the seawater sealed in Changxing Formation during burial period which is mixed by meteoric water and compacted porewater possibly from the bottom of Feixianguan Formation shales are the mainsources of the dolomitization fluids. Regional exposure in the late stage of Changxing formation carbonate sedimentation and buried karst are the main reasons for the formation of karst reservoirs. The high quality reservoirs in